Hydroxy group-containing modified polyester with polymerized lactone monomers

ABSTRACT

A hydroxy functional urethane modified polyester resin and solvent-based thermosetting coating composition comprising said resin and blocked polyisocyanate crosslinking agent. The coating composition may be formulated as a hot sprayable, high solids coating composition suitable for use as chip resistant automotive vehicle primer suitable for use on body panel areas subject to chipping by stones, gravel and other road debris. Alternatively, the composition may be formulated as a high solids composition sprayable with conventional spraying equipment. The hydroxy functional urethane modified polyester resin is the product of polymerization of lactone monomers in the presence of hydroxy-containing urethane modified polyester precursor. The polymerization reaction mixture comprises between about 10 and about 80 weight percent the hydroxy-containing urethane modified polyester precursor and between about 90 and about 20 weight percent lactone monomers.

Reference is made to related U.S. application Ser. No. 877,931 entitled"A Coating Composition of A Hydroxy Group--Containing Modified Polyesterwith Polymerized Lactone Monomers" filed Dec. 24, 1985 to Dervan et al.

TECHNICAL FIELD

This invention relates to a novel hydroxy functional urethane modifiedpolyester resin and to a novel, solvent-based, thermosetting coatingcomposition comprising same. It relates also to such coating compositionformulated, for example, as a hot sprayable, high solids coatingcomposition suitable for use as a chip resistant automotive vehicleprimer adapted for use on body panel areas subject to chipping bystones, gravel and other road debris.

BACKGROUND

Automobile manufacturers, in their efforts to extend the expected lifeof automobile sheet metal and the like, have directed considerableattention to various processes and compositions designed to result innot only improved corrosion resistance but also improved chip resistanceproperties. In particular, research and development efforts haverecently been directed to obtaining primer compositions which areflexible and chip resistant and which give corrosion protection whileexhibiting good humidity and solvent resistance, as well as goodintercoat adhesion. New automobile designs and concern about chipping inareas exposed to stones, gravel and other road debris, e.g. rockerpanels, have demanded such chip resistant primers which can be appliedin reasonable thicknesses by techniques which do not require extensiveand expensive processing modifications during painting operations. Todate available primers, whether high or low solids, have not provensuitable.

In order to overcome the aforementioned chipping problem it has beencommon to apply relatively thick chip resistant coatings in body panelregions which are inclined to chip, prior to application of stillanother primer composition. One such chip resistant sealer materialwhich has been employed is a polyvinyl chloride plastisol sealer whichhas been applied with airless spraygun equipment in thicknesses of about20 mils in regions subject to high levels of chipping. Problemsattendant with such thick coatings are readily apparent. Because of thethickness in the region to which it is applied, these materials presentan appearance problem often resulting in waviness and roughness in thefinal coating on the sheet metal. Often times surface imperfections alsoresult from the fact that a primer is applied over the top of thissealer, with the primer and sealer being cured together. As a resultsome solvent and plasticizer tend to be driven out of the polyvinylchloride plastisol and result in a wavy and rough surface. Still furtherproblems associated with the use of such polyvinyl chloride plastisolsealers and the like involve application technique. Since the polyvinylchloride plastisol sealers and the like must be applied in thicknessesof 20 mils or greater in order to obtain good adhesion, they cannot befeathered down to blend in with other regions of the sheet metal whichdo not require the additional chip protection. Thus, the materials mustbe applied using a masking technique whereby those regions which are notto be coated with the sealer material are masked in a separate operationprior to application of sealer. This masking is then removed after thesealer is applied. It would obviously be desirable to eliminate theseadditional steps in the application of the chip resistant sealermaterial.

Accordingly, it is a preferred object of this invention to provide anovel solvent based, thermosetting coating composition adapted for useas a chip resistant primer, which primer may be applied in thicknessesof less than 20 mils and which may be feathered in such a manner as toblend with paint in other areas of the substrate to be painted which donot require chip resistant coating.

It is a further object of the present invention to provide novel resinssuitable for use in solvent-based thermosetting coating compositions. Inthis regard, it is a particular object of the invention to providenovel, hydroxy functional urethane modified polyester resins which arecrosslinkable during cure on the surface of a substrate.

It is another object of the invention to provide novel coatingcompositions which comprise crosslinkable hydroxy functional urethanemodified polyester resin and blocked polyisocyanate crosslinking agentand which provide high crosslinking efficiency and tough, well curedfilms at minimum bake temperatures such as when applied as automotiveprimers. In this regard, it is a particular object of the invention toprovide a novel hydroxy functional urethane modified polyesterresin/blocked polyisocyanate thermosetting coating composition ofsufficiently low Volatile Organic Content (VOC) to aid in meetinggovernmental emissions guidelines and yet which can be applied to asubstrate by spraying or other known method.

It is still another object of the invention to provide a compositionwhich will form a coating on a substrate, which coating has advantageousphysical properties including, for example, humidity and solventresistance, flexibility and corrosion protection for the underlyingsubstrate.

Additional aspects and advantages of the invention will be apparent fromthe following description thereof.

DISCLOSURE OF THE INVENTION

According to the present invention, novel crosslinkable hydroxyfunctional urethane modified polyester resins are provided which aresuitable for use in thermosetting coating compositions, and which areespecially advantageous for use in high solids and chip resistant,organic solvent based thermosetting coating compositions. The hydroxyfunctional urethane modified polyester resins of the inventionpreferably have a number average molecular weight (Mn) of about 2,000 toabout 20,000 and are the product of polymerization of lactone monomersin the presence of hydroxy-containing urethane modified polyesterprecursor preferably (i) having a number average molecular weight (Mn)between about 1,000 and about 10,000, (ii) having a hydroxy numberbetween about 30 and about 300, and (iii) containing between about 1 andabout 10 urethane groups per molecule. The polymerization of the lactonemonomers is preferably carried out at a temperature between about 50° C.and about 300° C. The polymerization reaction mixture comprises betweenabout 10 and about 80 weight percent hydroxy-containing urethanemodified polyester precursor and between about 90 and about 20 weightpercent lactone monomers.

A first preferred type of such hydroxy-containing urethane modifiedpolyester precursor suitable for forming the hydroxy functional resin ofthis invention is the reaction product of:

(A) urethane modified diol being the reaction product of: (a) diol and(b) diisocyanate, wherein the diol and diisocyanate are reacted in amolar ratio of from about 4:1 to about 4:3, respectively;

(B) polyol comprising at least about 5 weight percent triol; and

(C) acid component selected from dicarboxylic acids and anhydridesthereof.

Preferably, this first preferred type of such precursor has a hydroxylnumber between about 30 and about 200.

A second preferred type of such hydroxyl-containing urethane modifiedpolyester precursor suitable for forming the hydroxy functional resin ofthis invention is the reaction product of:

(A) hydroxy functional polyester resin being the reaction product of:(a) polyhydroxy material comprising diols and triols and (b) acidcomponent selected from dicarboxylic acids and anhydrides thereof,wherein (a) and (b) are reacted in amounts so as to provide hydroxylgroups and carboxyl groups in a ratio of from about 6:2 to about 6:5,respectively; and

(B) diisocyanate, wherein (A) and (B) are reacted in amounts so as toprovide hydroxyl groups and isocyanate groups in a ratio of from about4:1 to about 10:1, respectively.

Preferably, this second preferred type of such precursor has a hydroxylnumber between about 50 and about 250 and contains between about 1 andabout 7 urethane groups per molecule. Preferably, the polyhydroxymaterials comprise diols and triols in a hydroxyl equivalent ratio offrom about 4:1 to about 1:4, respectively, more preferably this ratio isabout 3:1 to about 3:2.5.

Also according to the present invention, a novel, organic solvent based,thermosetting resin/crosslinking agent composition, in addition tosolvent and any pigments and additives such as, for example, catalyst,flow control agents and the like, comprises the hydroxy functionalurethane modified polyester resin of the invention and blockedpolyisocyanate crosslinking agent preferably selected from the groupconsisting of, but not necessarily limited to, blocked trifunctionalisocyanurate ring containing polyisocyanates and oligoester modifiedblocked isocyanates.

Particularly preferred compositions of the invention are thoseformulated as high solids coating compositions having solids levels inthe range of 65-80% solids and which are applied as chip resistantprimers in those areas of automotive panels, such as rocker panels,which are exposed to high levels of chipping. Such compositions may beapplied in thicknesses ranging from 1 to 25 mils wet to obtain finalcoatings in the range of 1 to 12 mils dry, and may be feathered down toblend in with paint applied to regions outside that requiring additionalchip resistance protection. Generally, the compositions of this solidslevel may be applied using hot spray equipment at temperatures in therange of room temperature, i.e., about 70° F., to about 160° F.

Other preferred compositions of the invention are those formulated ashigh solids coating compositions adapted to be applied by conventionalspraying onto a substrate. These high solids coating compositions mayhave a solids level in the range of 50-60% and are especially useful asa primer coating on the bare, unpolished metal surface of an automotivevehicle. As used herein, a high solids coating composition is one havinga volatile organic content of about 479 g/l (4.0 lb./gal.) or less.

Other features and advantages of this invention will become moreapparent from the following, detailed description thereof including thepreferred embodiments and best mode of carrying out this invention.

DETAILED DESCRIPTION OF THE INVENTION

More specifically, the invention relates to a novel hydroxy functionalurethane modified polyester resin suitable for use in a thermosettingcoating composition and to a thermosetting coating compositioncomprising that hydroxy functional resins and a blocked polyisocyanatecrosslinking agent.

The novel, hydroxy functional urethane modified polyester resinpreferably has a number average molecular weight (Mn) between about2,000 and about 20,000, preferably between about 2,000 and about 6,000,and is the product of polymerization of lactone monomers in the presenceof hydroxy-containing urethane modified polyester precursor (i) having anumber average molecular weight (M_(n)) between about 1,000 and about10,000, (ii) having a hydroxyl number of 30-300, and (iii) containingbetween about 1 and about 10 urethane groups per molecule. One preferredtype of precursor suitable for use in this invention is the reactionproduct of urethane modified diols with polyol and acid component. Asecond preferred type of precursor suitable for use in this invention isthe reaction product of polyester polyol resins with diisocyanate. Thepolymerization of lactone monomers with the precursor is preferablycarried out at a temperature between about 50° C. and about 300° C.,more preferably at a temperature of between about 130° C. and about 200°C. The polymerization reaction mixture comprises between about 10 andabout 80 weight percent hydroxy-containing urethane modified polyesterprecursor and between about 90 and about 20 weight percent lactonemonomers. Preferably, the polymerization reaction mixture comprisesbetween about 35 and about 65 weight percent hydroxy-containing urethanemodified polyester precursor and between about 65 and 35 weight percentlactone monomers.

Thermosetting compositions of the invention comprise the above hydroxyfunctional urethane modified polyester resin and blocked polyisocyanatecrosslinking agent comprising at least two isocyanate groups which havebeen blocked by reaction with an active hydrogen bearing blocking agent.The blocked polyisocyanate crosslinking agent is included in thecomposition in an amount such that upon deblocking of the blockedisocyanate groups thereof at the cure temperature of the composition,the crosslinking agent provides between about 0.5 and about 1.6 reactiveisocyanate groups per hydroxy group on the hydroxy functional urethanemodified polyester resin.

Each of the above major components of the compositions as well as othercomponents and other aspects of the invention are described hereinafterin greater detail.

A. Hydroxy Functional Urethane Modified Polyester Resin

As described above, this copolymer is the product of polymerization oflactone monomer in the presence of hydroxy-containing urethane modifiedpolyester precursor.

It is believed to be a significant characterizing aspect of the hydroxyfunctional urethane modified polyester resin of the invention that thepolymerized lactone portion of this hydroxy functional resin gives theresin flexibility as well as toughness, two key properties when choosinga primer for use in areas susceptible to chipping. Still further,because the hydroxy functional urethane modified polyester resins of theinvention are branched, they require a minimum amount of crosslinking inorder to obtain a suitable network for good coating integrity.

Each of the reactants employed in the preparation of the hydroxyfunctional urethane modified polyester resin is described in greaterdetail below.

(i) Hydroxy-Containing Urethane Modified Polyester Precursor

The hydroxy-containing urethane modified polyester precursor employed tomake the hydroxy functional urethane modified polyester resins of theinvention (i) have a number average molecular weight (M_(n)) betweenabout 1,000 and about 10,000, (ii) have a hydroxyl number between about30 and about 300, and (iii) contain between about 1 and about 10urethane groups per molecule. Two preferred types of precursors suitablefor use in forming the hydroxy functional resin of this invention arehereinafter described in detail. While two preferred types of precursorsare disclosed herein, this disclosure is not meant to limit theprecursor to these preferred types. Other hydroxy-containing urethanemodified polyester precursor suitable for use in forming the hydroxyfunctional resin of this invention will be apparent to those of the artin view of the present disclosure.

A first preferred type of precursor suitable for use in forming thehydroxy functional urethane modified polyester resin of this inventionis the reaction product of:

(A) urethane modified diol being the reaction product of: (a) diol and(b) diisocyanate, wherein the diol and the diisocyanate are reacted in amolar ratio of from about 4:1 to about 4:3, respectively;

(B) polyol comprising at least about 5 weight percent triol; and

(C) acid component selected from dicarboxylic acids and anhydridesthereof.

In forming the urethane modified diol, the diol and diisocyanate arepreferably reacted in a molar ratio of from about 2:0.8 to about 2:1.2,respectively, most preferably in a 2:1 molar ratio. This first type ofprecursor, which is the reaction product of urethane modified diol,polyol and acid component, preferably has a number average molecularweight (M_(n)) between about 2,000 and about 4,000 and a hydroxyl numberpreferably between about 30 and about 200. Most preferably the hydroxylnumber is between about 50 and about 120.

The diols employed in making the urethane modified diol include, but arenot limited to, alkylene glycols, such as butylene glycol, neopentylglycol, 1,5-pentene glycol, 3-cyclohexene-1,1-dimethynol, other glycolssuch as hydrogenated bisphenol A, caprolactone diol (e.g., the reactionproduct of caprolactone and ethylene glycol), hydroxy alkylatedbisphenols, polyether glycols, e.g., poly(oxytetramethylene)glycol, andpolyester diols, e.g.,2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, and thelike. Preferred diols are neopentyl glycol and2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxy-propionate, thelatter material being commercially available as Esterdiol 204(trademark, Union Carbide Corp., Danbury, Conn.). While various types ofdiols have been mentioned above as suitable for use as the diolcomponent in making the urethane modified diol, their disclosure is notmeant to be limiting. Selection of other diols which would be suitablefor use in forming the urethane modified diol would be well within theskill of those in the art in view of the present disclosure. Mixtures ofdiols may also be employed in making the urethane modified diol. Stillfurther, in view of the principles discussed above for forming theurethane modified diol, one skilled in the art would appreicate thattriols may be used in place of the diols to form urethane modifiedtriols which may be employed herein.

The diisocyanate employed in making the urethane modified diol may beessentially any diiocyanate and numerous diisocyanates are well known inthe art. The diisocyanate may be any of a number of aliphatic,cycloaliphatic, and aromatic diisocyanates, such as those selected fromthe group which includes, but which is not limited to, hydrocarbondiisocyanates and substituted hydrocarbon diisocyanates, such as1,6-hexamethylene diisocyanate, isophorone diisocyanate, p-phenylenediisocyanate, biphenyl diisocyanate, toluene diisocyanate, and3,3-dimethyl-4,4-biphenylene diisocyanate. As would be apparent to thoseskilled in the art in view of the present disclosure, mixtures ofvarious diisocyanates also may be employed as the diisocyanate componentused in forming the urethane modified diol.

The polyol component, used in forming the first preferredhydroxy-containing urethane modified polyester precursor describedabove, comprises at least about 5 weight percent triol (based on theweight of the polyol component). Preferred triols are conventional lowmoleclar triols such as 1,2,6-hexane triol, 1,1,1-trimethylol propane,3-(2-hydroxy-propoxy)-1,2-propanediol and polycaprolactone triols, whichare commercially available as, for example, TONE-301 (trademark, UnionCarbide Corp., Danbury, Conn.). This polyol component may also comprise,in addition to the triols, other polyol materials such as diols ortetrols. Preferably, however, these other polyols, when employed,consist of diols. Examples of suitable diols which may be included inthe polyol component are those which have been disclosed above assuitable for forming the urethane modified diol. Preferred diols for usein the polyol component are linear aliphatic diols. While the polyolcomponent may comprise materials such as diols in addition to the triolsthe polyol component may consist essentially of triols. By employingdiols in the polyol component in addition to the triols the flexibilityof the coating composition is generally increased. Thus, selection ofthe polyol component to be used in forming the first preferredhydroxy-containing urethane modified polyester precursor will bedependent on the particular desired properties and application of thecoating compositon. When diols are employed in the polyol component, thepolyol preferably comprises from about 10 to about 80 weight percenttriols and from about 90 to about 20 weight percent diols.

The acid component used to form the first preferred hydroxy-containingurethane modified polyester precursor is selected from the goupcomprising aliphatic, aromatic, and cycloaliphatic dicarboxylic acidsand anhydrides thereof. Numerous examples of such dicarboxylic acids andanhydrides are well known to those in the art. Preferably the acidcomponent is selected from the group comprising C₆ -C₄₀ dicarboxylicacids and anhydrides thereof, which group includes, but is not limitedto, adipic acid, azelaic acid, sebasic acid, dodecane dicarboxylic acid,dimer acid and cyclohexane dicarboxylic acid and anhydrides thereof.Mixtures of suitable acids and/or their anhydrides may also be used asthe acid component in forming this precursor.

In forming the first preferred type of hydroxy-containing urethanemodified polyester precursor, the diol (a) and the diisocyanate (b) arecombined and reacted, generally at an elevated temperature, so as toform the urethane modified diol. The ratio of the diol to diisocyanate(i.e., a molar excess of diol) is such that at the completion of thisreaction substantially no unreacted isocyanate groups are present. Thisurethane modified diol is then combined and reacted with the polyol andacid component, generally in the presence of a catalyst and at elevatedtemperatures, so as to effect formation of the hydroxy-containingurethane modified polyester precursor. Catalysts desirably assure arapid and/or more complete carboxyl/hydroxyl condensation reaction.Examplary of catalysts which may be so employed are dibutyl tin oxide,hydrated monobutyl tin oxide, butylchlorotin dihydroxide, butyl tintris(2-ethylhexoate), tetraisopropyl titanate, strong acids such asp-toluene sulfonic acid, phosphoric acid, sulfuric acid, and materialssuch as zinc oxide, antimony oxide (Sb₂ O₃) and sodium acetate. Stillother catalysts useful for this purpose will be apparent to thoseskilled in the art in view of the present disclosure.

A second preferred type of precursor suitable for forming the hydroxyfunctional resins of this invention is the reaction product of:

(A) hydroxy functional polyester resin being the reaction product of:(a) polyhydroxy material comprising diols and triols with (b) acidcomponent selected from dicarboxylic acids and anhydrides thereof,wherein (a) and (b) are reacted in amounts so as to provide hydroxylgroups and carboxyl groups in a ratio from about 6:2 to about 6:5,respectively; and

(B) diisocyanate, wherein (A) and (B) are reacted in amounts so as toprovide hydroxyl groups and isocyanate groups in a ratio of from about4:1 to about 10:1, respectively.

Preferably, the polyhydroxy materials comprise the diols and triols in ahydroxyl equivalent ratio from about 4:1 to about 1:4, respectively,more preferably from about 3:1 to about 3:2.5. By hydroxyl equivalentratio is meant the ratio of the hydroxyl equivalents of the diol to thehydroxyl equivalents of the triol. This second preferred type ofprecursor, which is the reaction product of hydroxy functional polyesterresin and diisocyanate, preferably has a number average molecular weight(M_(n)) between about 2000 and about 4000 and a hydroxyl numberpreferably between about 50 and about 250, and preferably containsbetween about 1 and about 7 urethane groups per molecule.

The diols, triols, acid components and diisocyanates which are employedin forming this second preferred type of hydroxy-containing urethanemodified polyester precursor may be selected from such reactantsdescribed above for making the first preferred type ofhydroxy-containing urethane modified polyester precursor. Theirdisclosure is not, however, meant to be limiting. Still other diols,triols, acid components and diisocyanates which may be employed in thisinvention in forming this second preferred type of precursor would beapparent to those of the art in view of the present disclosure. Informing this second preferred type of precursor, the polyhydroxymaterials (i.e., diols, triols and optionally tetrols, etc.) and acidcomponent are combined and reacted, generally at elevated temperaturesand in the presence of a catalyst, so as to effect formation of ahydroxy functional polyester resin. Catalysts useful to accelerate thecarboxyl/hydroxyl condensation reaction are well known in the art.Suitable carboxyl/hydroxyl catalysts have been previously disclosedherein. Others are known to those of the art. This hydroxy functionalpolyester resin is then modified by reaction with the diisocyanate,whereby urethane groups are incorporated into the polyester resinforming the second preferred type of hydroxy-containing urethanemodified polyester precursor. p The reactions, whereby either the firstor second preferred type of precursor is formed, are generally carriedout in the presence of solvents commonly employed for coatingformulations such as toluene, xylene, methyl amyl ketone, etc.

Other suitable hydroxy-containing urethane modified polyester precursorsare commercially available and known to those skilled in the art andwould be apparent in view of this disclosure.

(ii) Lactone Monomers

The lactone reactant may be any lactone, or combination of lactones,having at least six carbon atoms, for example, from six to eight carbonatoms, in the ring and at least one hydrogen substituent on the carbonatom which is attached to the oxy group in said ring. In one aspect, thelactone used as a reactant can be represented by the general formula:##STR1## in which n is at least four, for example, from four to six, atleast n+2R's are hydrogen, and the remaining R's are substituentsselected from the group consisting of hydrogen, alkyl, cycloalkyl,alkoxy and single ring aromatic hydrocarbon radicals. Lactones havinggreater numbers of substituents other than hydrogen on the ring, andlactones having five or less carbon atoms in the ring, are consideredunsuitable for the purpose of the invention because of the tendency thatpolymers thereof have to revert to the monomer, particularly at elevatedtemperature.

The lactones preferred in this invention are the epsilon-caprolactoneshaving the general formula: ##STR2## wherein at least six of the R's arehydrogen and the remainder are hydrogen, alkyl, cycloalkyl, alkoxy orsingle ring aromatic hydrocarbon radicals, none of the substituentscontain more than about twelve carbon atoms, and the total number ofcarbon atoms in the substituents on a lactone ring does not exceed abovetwelve. Unsubstituted epsilon-caprolactone, in which all the R's arehydrogen, is derived from 6-hydroxyhexanoic acid and is most preferred.Substituted epsilon-caprolactones, and mixtures thereof, are availableby reacting a corresponding substituted cyclohexanone with an oxidizingagent such as peracetic acid.

Among the substituted epsilon-caprolactones considered most suitable forthe purposes of the invention are the various monoalkylepsilon-caprolactones such as the monomethyl-, monoethyl-, monopropyl-,monoisopropyl-, etc. to monododecyl epsilon-caprolactones; dialkylepsilon-caprolactones in which the two alkyl groups are substituted onthe same or different carbon atoms, but not both on the epsilon carbonatom; trialkyl epsilon-caprolactones in which two or three carbon atomsin the lactone ring are substituted, so long as the epsilon carbon atomis not distributed; alkoxy epsilon-caprolactones such as methoxy andethoxy epsilon-caprolactones; and cycloalkyl, aryl, and aralkylepsilon-caprolactones such as cyclohexyl, phenyl and benzylepsilon-caprolactones.

Lactones having more than six carbon atoms in the ring, e.g.,zeta-enatholactone and eta-caprylolactone may also be polymerized inaccordance with the invention.

Polymerization of the lactones in accordance with this invention iscarried out in conventional manner in that the polymerization isinitiated by reaction with a compound having at least one reactivehydrogen capable, with out without the aid of a catalyst, of opening thelactone ring and adding it as an open chain without forming water ofcondensation--in this case the initiator compound being the hydroxyfunctional urethane modified polyester precursor described above.

The polymerization reaction mixture comprises between about 10 and about80 weight percent of the above described hydroxy functional urethanemodified polyester precursor and between about 10 and about 20 weightpercent of the lactone monomers. Preferably, the polymerization reactionmixture comprises between 35 and about 65 weight percent of the hydroxyfunctional urethane modified polyester precursor and between about 65and about 35 weight percent of the lactone monomers.

To initiate and continue the polymerization of the lactone, the lactoneand the initiator (i.e., the precursor) are preferably heated to atemperature between about 130° and 200° C. in order to achieve apractical and desirable rate of reaction with a minimum ofdecomposition. The temperature may be considerably lower however, i.e,as low as about 50° C. at the sacrifice of speed of reaction. It mayalso be considerably higher, i.e., up to about 300° C., although caremust be taken at such higher temperatures because of the more likelylosses, at temperatures above 250° C., due to decomposition orundesirable side reactions. Generally, therefore, a temperature range of50° to 300° C. is considered operable and a more limited range betweenabout 130° and 200° C. is considered preferable.

The polymerization may be, and preferably is, carried out with the useof a catalyst, such as a basic or neutral ester interchange catalyst, toaccelerate the reaction. Among catalyst suitable for this purpose aresuch metals as lithium, sodium, potassium, rubidium, cesium, magnesium,calcium, barium, strontium, zinc, aluminum, titanium, cobalt, germanium,tin, lead, antimony, arsenic and cerium, as well as the alkoxidesthereof. Additional suitable catalysts are, by way of example, thecarbonates of alkali- and alkaline earth metals, zinc borate, leadborate, zinc oxide, lead silicate, lead arsenate, litharge, leadcarbonate, antimony trioxide, germanium dioxide, cerium trioxide,cobaltous acetate and aluminum isopropoxide. Catalyst concentrationsbetween about 0.001 and 0.5%, based on the weight of the startinglactones, are suitable. The preferred range is from 0.01 to 0.2%.

The hydroxy functional urethane modified polyester resin polymerizationproducts obtained in accorance with the invention have number averagemolecular weights (Mn) generally upwards of about 2,000, preferablywithin the range of about 2,000 to about 20,000, although number averagemolecular weights below and substantially above this range areobtainable if desired. Most preferably, the resin polymerizationproducts have a number average molecular weight between about 2,000 andabout 6,000. Also, while not wishing to be bound by theory, it presentlyis understood that the chemical structure of the hydroxy functionalurethane modified polyester resin is as follows. They have reactiveterminal hydroxyl groups. Further, it presently is understood that theyare characterized by the presence of series of interconnected,substantially linear units or groups composed of carbon, hydrogen andoxygen. The interconnected units are opened lactone residues each havinga terminal oxy group at one end, a carbonyl group at the other end, anintermediate chain of at least five carbon atoms and at least onehydrogen substituent on the carbon atom in the intermediate chain thatis attached to the terminal oxy group. The oxy group of one lactoneresidue is connected to the carbonyl group of an adjacent lactoneresidue in the series and the oxy group of the last lactone residue in aseries is connected to a hydrogen to form a terminal hydroxyl group atone end of the series.

B. Crosslinking Agent

The crosslinking agent employed in the novel solvent based coatingcompositions of the invention comprises blocked polyisocyanate. Thenovel solvent based coating compositions of the invention, as a resultof employing blocked polyisocyanate crosslinking agents, exhibitexceptional shelf stability even when corrosion inhibiting pigments suchas zinc chromate are used in high concentrations.

As used herein "blocked polyisocyanate" means an isocyanate compoundcontaining two or more isocyanate groups, all of which have been reactedwith a material which will prevent reaction of the isocyanate group atroom temperature with compounds that conventionally react with suchgroups, and at least some of which will permit that reaction to occur athigher (cure) temperatures. In general the blocked polyisocyanate may beprepared by reacting a sufficient quantity of an active hydrogencontaining blocking agent with the polyisocyanate to insure that no freeisocyanate groups are present. The blocking agent may be represented bythe formula BH and may be selected from numerous materials, hereinafterdiscussed, which bear an active hydrogen.

The blocked polyisocyanate crosslinking agent is included incompositions of the invention in amounts such that upon deblocking ofthe blocked isocyanate groups at the cure temperature of thecomposition, the crosslinking agent provides between about 0.5 and about1.6, preferably between about 0.8 and about 1.3, reactive isocyanategroups per hydroxy group on the film forming hydroxy functional urethanemodified polyester resin of the coating composition as described above.Blocked polyisocyanates of numerous types may be employed in thecompositions of the invention. Particularly suitable blockpolyisocyanates, which will be discussed further hereinafter, are thoseselected from the group consisting of blocked polymethylene polyphenolisocyanates, isocyanurate ring containing block polyisocyanates andcertain oligoester modified blocked polyisocyanates.

In the preparation of the blocked polyisocyanate crosslinking agent, anysuitable organic polyisocyanate may be used. Representative examples arethe aliphatic compounds such as trimethylene, tetramethylene,pentamethylene, hexamethylene, 1,2-propylene, 1,2-butylene,2,3-butylene, 1,3-butylene, ethylidine and butylidene diisocyanates; thecycloalkylene compounds such as 1,3-cyclopentane, 1,4-cyclohexane, and1,2-cyclohexane diisocyanates; the aromatic compounds such asm-phenylene, p-phenylene, 4,4'-diphenyl, 1,5-naphthalene, and1,4-naphthalene diisocyanates, the aliphatic-aromatic compounds such as4,4'-diphenylene methane, 2,4- or 2,6-tolylene, or mixtures thereof,4,4'-toluidine, and 1,4-xylylene diisocyanates; substituted aromaticcompounds such as dianisidine diisocyanate, 4,4'-diphenyletherdiisocyanate and chlorodiphenylene diisocyanate; the triisocyanates suchas triphenyl methane-4,4,4"-triisocyanate, 1,3,5-triisocyanate benzeneand 2,4,6-triisocyanate toluene; the tetraisocyanates such as4,4'-diphenyl-dimethyl methane-2,2',5,5'-tetraisocyanate; and thepolymerized polyisocyanates such as tolylene diisocyanate dimers andtrimers, and the like.

In addition, the organic polyisocyanate may be a prepolymer derived froma polyol including polyether polyol or polyester polyol, includingpolyesters which are reacted with excess polyisocyanates to formisocyanate-terminated prepolymers. The polyols may be simple polyolssuch as glycols, e.g., ethylene glycol and propylene glycol, as well asother polyols such as glycerol; trimethylolpropane, pentaerythritol, andthe like, as well as mono-ethers such as diethylene glycol, tripropyleneglycol and the like and polyethers, i.e., alkylene oxide condensates ofthe above. Among the alkylene oxides that may be condensed with thesepolyols to form polyethers are ethylene oxide, propylene oxide, butyleneoxide, styrene oxide and the like. These are generally calledhydroxyl-terminated polyethers and can be linear or branched. Examplesof polyethers include polyoxyethylene glycol, polyoxypropylene glycol,polyoxytetramethylene glycol, polyoxyhexamethylene glycol,polyoxynonamethylene glycol, polyoxydecamethylene glycol,polyoxydodecamethylene glycol and mixtures thereof. Other types ofpolyoxyalkylene glycol ethers can be used. Especially useful polyetherpolyols are those derived from reacting polyols such as ethylene glycol,diethylene glycol, triethylene glycol, 1,4-butylene glycol, 1,3-butyleneglycol, 1,6-hexanediol, and their mixtures; glycerol, trimethylolethane,trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol,dipentaerythritol, tripentaerythritol, polypentaerythritol, sorbitol,methyl glucosides, sucrose and the like with alkylene oxides such asethylene oxide, propylene oxide, their mixtures, and the like.

A particular class of aromatic polyisocyanates which may be employed inthe novel solvent based coating compositions of the invention arepolymethylene polyphenol isocyanates having the general formula:##STR3## wherein n equals 1 to 3. Such compounds, sold under thetradename "PAPI" by the UpJohn Chemical Company of Kalamazoo, Mich.,have proven to be particularly useful in compositions of the invention,resulting in compositions exhibiting desirable toughness in the finalcured coating.

The active hydrogen containing blocking agents which are reacted withthe above described organic diisocyanates may be selected from numerousblocking agents which will be apparent to those skilled in this art.Representative of those blocking agents which are preferred are thoseselected from the group consisting of (i) aliphatic, cycloaliphatic andaromatic alkyl monoalcohols; (ii) hydroxy amines; (iii) oximes; (iv)lactams; and (v) triazoles. Any suitable aliphatic, cycloaliphatic oraromatic alkyl monoalcohol may be used as a blocking agent in accordancewith the present invention. For example, aliphatic alcohols, such asmethyl, ethyl, chloroethyl, propyl, butyl, amyl, hexyl, heptyl, octyl,nonyl, 3,3,5-trimethylhexyl, decyl, and lauryl alcohols, and the likemay be employed. Suitable cycloaliphatic alcohols include, for example,cyclopentanol, cyclohexanol and the like, while aromatic-alkyl alcoholsinclude phenylcarbinol, methylphenylcarbinol, and the like. Minoramounts of even higher molecular weight relatively non-volatilemonoalcohols may be used, if desired, to serve as plasticizers in thecoatings provided by the invention. Examples of hydroxyl amines whichmay be employed as blocking agents include ethanol amine and propanolamine. Suitable oxime blocking agents include, for example,methylethylketone oxime, acetone oxime and cyclohexanone oxime. Examplesof lactams which may be used as blocking agents are epsilon-caprolactam,epsilon-butyrolactam and pyrrolidone, while suitable triazoles includecompounds such as 1,2,4-triazole, 1,2,3-benzotriazole, 1,2,3-tolyltriazole and 4,5-diphenyl-1,2,3-triazole. Particularly preferred activehydrogen containing blocking agents are methylethyl ketoxime and2-ethylhexanol.

(i) Isocyanurate Ring Containing Blocked Isocyanate Compounds

Within the scope of the above general class of blocked polyisocyanatecrosslinking agents, a particular class type of blocked polyisocyanatecrosslinking agent which may be employed in the noval solvent basedcoating compositions of the invention comprises isocyanurate ringcontaining blocked isocyanate compounds. In general, these blockedpolyisocyanates may be formed by blocking with the aforementionedblocking agent isocyanurate ring containing polyisocyanates. Thesecompounds may be formed by cyclotrimerization of difunctionalisocyanates. Usually, the reaction does not stop in this stage andcontinues through the formation of polyfunctional oligomers or a mixtureof such oligomers with a portion of the pure trifunctionalpolyisocyanate. Mixtures of trifunctional product and variouspolyfunctional oligomers are commercially available.

A particularly desirable blocked polyisocyanate crosslinking agent isthe blocked form of the pure trifunctional isocyanurate represented bythe following formula: ##STR4## wherein R is selected from the groupconsisting of aliphatic, cycloaliphatic and aromatic groups andcombinations thereof and B is the residue of an active hydrogencontaining blocking agent. More specifically, this compound is disclosedin U.S. Pat. No. 4,491,663, the disclosure of which is herebyincorporated by reference.

(ii) Oligoester Modified Blocked Polyisocyanates

Still further particular blocked polyisocyanates useful as crosslinkingagents in the novel solvent based coating composition of this inventionare oligoester modified block polyisocyanates prepared from a particularclass of oligoester diols and triols. A first type of such oligoestermodified blocked polyisocyanates is prepared from organic diisocyanatesbearing one isocyanate group more reactive than the other, with the morereactive isocyanate first being blocked with a blocking agent and theremaining isocyanate group then being reacted with hydroxylfunctionality of an oligoester diol or triol as referred to above. Thesecond type of oligoester modified blocked polyisocyanate may beprepared by reacting oligoester diols from the aforementioned class ofoligoesters with an excess of organic diisocyanate so as to form anisocyanate terminated prepolymer followed by blocking of the terminalisocyanate groups of the prepolymer with an active hydrogen containingblocking agent. Each of these materials is particularly useful in thecompositions of the invention and produces final cured coatingcompositions exhibiting outstanding flexibility.

Oligoesters of the type employed in the preparation of thesecrosslinking agents are described in U.S. Pat. No. 4,322,508 issued Mar.30, 1982, the disclosure of which is hereby incorporated by reference.The hydroxy functional oligoesters within the useful class of materials(i) have a number average molecular weight (M_(n)) between about 150 andabout 3000, preferably between about 230 and about 1000, (ii) bear 2 or3 hydroxyl groups per molecule, and (iii) are formed by anesterification reaction between a carboxylic acid and an epoxide. Theesterification reaction products are selected from the group consistingof:

(a) the esterification reaction product of polycarboxylic acid, i.e.,carboxylic acid bearing 2 or more carboxyl groups, and monoepoxide;

(b) the esterification reaction product of polyepoxide, i.e., a compoundhaving 2 or more epoxide groups, and monocarboxylic acid, preferablycontaining no ethylenic unsaturation, and bearing no hydroxyfunctionality;

(c) the esterification reaction product of hydroxy functional carboxylicacid and mono- or polyepoxide, preferably monoepoxide;

(d) the esterification reaction product of monocarboxylic acid andhydroxy functional mono- or polyepoxide, preferably monoepoxide; and

(e) mixtures of (a)-(d).

As noted above, the first type of oligoester modified blockedpolyisocyanate crosslinking agent is prepared by (i) reacting organicdiisocyanate bearing one isocyanate group which is more reactive thanthe other with a sufficient amount of an active hydrogen containingblocking agent to react substantially with all of the more reactiveisocyanate groups, thus providing a half-blocked diisocyanate and (ii)reacting this half-blocked intermediate with the above discussedoligoester. The organic diisocyanates employed in this synthesis, aswell as the active hydrogen containing blocking agents, are discussedabove in connection with the preparation of the isocyanurate ringcontaining blocked isocyanate crosslinking agents useful in compositionsof the invention. The organic polyisocyanate-blocking agent adductintermediate is formed by reacting a sufficient quantity of the blockingagent with the organic diisocyanate to insure that one of the two --NCOgroups on the diisocyanate is reacted. The reaction between the organicdiisocyanate and the blocking agent is exothermic; therefore, thediisocyanate and the blocking agent are preferably admixed attemperatures no higher than about 80° C., preferably below about 50° C.,to minimize the exothermic effect.

This intermediate is next reacted with the oligoester diol or trioldescribed above so as to react substantially all free or unblockedisocyanate groups of the diisocyanate/blocking agent intermediate withhydroxyl groups of the oligoester. This reaction is carried outdesirably at a temperature of about 80°-120° C.

As also discussed above, the second type of oligoester modified blockedpolyisocyanate crosslinking agent useful in the novel solvent basedcoating compositions of the invention is prepared by reacting an excessof organic diisocyanate with an oligoester diol from the above describedclass of oligoesters followed by reaction of the terminal isocyanategroups formed on the resultant prepolymer with an active hydrogencontaining blocking agent as described above so as to react withsubstantially all the isocyanate groups. The diisocyanate startingmaterial is used in excess in amounts sufficient to insure that theintermediate is isocyanate terminated. Therefore, it is preferable thatthe organic diisocyanates and the dihydroxy functional oligoester bereacted in a molar ratio of from greater than 1:1 up to 2:1. Numerousdiisocyanates of the type described hereinbefore may be employed in thepreparation of this intermediate. While it is not necessary that oneisocyanate group be more reactive than the other, the preparation ofthis type of crosslinking agent does not preclude the use of suchmaterial.

C. General Discussion--Other Aspects of Invention and Other Components

The coating compositions of the invention have been found to provide acured coating having the advantageous physical properties describedabove, over a wide range of cure temperatures and a wide range of solidslevels. More specifically, the coating compositions according topreferred embodiments of the invention have been found to cure attemperatures from as low as about 120° C. or less within about 15minutes or less, and yet to cure and suffer no significant loss ofadvantageous physical properties at temperatures as high as about 200°C. or more for periods up to about 60 minutes or more. Consideredtogether with the storage stability of the coating composition, it canbe readily recognized that the present invention provides a highlysignificant advance in the coating composition art.

It will be within the skill of the art to determine the proper VolatileOrganic Content (VOC) for a given coating composition of the inventionand for a given application. Preferred solvents have relatively lowvolatility at temperatures appreciably below their boiling points suchthat solvent evaporation is low during storage and/or application of thecoating composition to the substrate. A suitable solvent system mayinclude, for example, toluene, methyl ethyl ketone, isobutyl acetate,xylene, cellosolve acetate, acetone and a mixture of any of them. Othersolvents which may be employed include terpenes, aliphatic and aromaticnaphthas, and the like. Additional suitable solvents are commerciallyavailable and will be apparent to the skilled of the art in view of thepresent disclosure.

Any solvent allowed to remain in the cured coating should be inert so asto avoid adverse effect upon the cured coating or upon another coatinglayer used in conjunction with it during the curing process orthereafter. Preferrably, the cured coating is substantially free ofsolvent.

Sufficient solvent is used to reduce the viscosity of the coatingcomposition to a level suitable for application to the substrate in thedesired manner.

Obviously, in those cases where the composition is to be applied as achip resistant primer the amount of solvent will be reduced so as togive a solids level of about 65-80%. Such higher solids materials aregenerally applied using hot spray equipment.

Flow control agent(s), for example, polybutyl acrylate; wettingagent(s), for example, silicone; pigments; pigment dispersants;corrosion inhibitors, for example, chromate pigments, numerous of all ofwhich are known to the skilled of the art, may be employed in thecoating compositions of the invention. In addition, suitable reactiveadditives can be used, including, for example, low molecular weight diolflow control agents and reactive diluents.

Compositions of the invention, and in particular the chip resistantprimers of the invention, may also include anti-settling or anti-saggingagents to control the thixotropic properties of the composition.Exemplary of available materials suitable for this purpose are Dislon(trademark) 6900-20X manufactured by Kusumoto Chemicals, Ltd., Tokyo,Japan and sold by King Industries, Norwalk, CT 06852; Bentone(trademark) 38, N. L. Industries, Highstown, N.J. 08520; and Cab-O-Sil(trademark) M-5, Cabot Corporation, Boston, Mass.

Curing the coating composition requires baking for sufficient time atsufficiently elevated temperature to react the crosslinking agent withthe hydroxyl functionality of the hydroxy functional urethane modifiedpolyester resins. The time and temperature required to cure the coatingare interrelated and depend upon the particular hydroxy functionalurethane modified polyester resin, crosslinking agent, solvent and othermaterials, if any, and the amount of each comprising the coatingcomposition. The coating compositions according to preferred embodimentsof the invention, as described above, have been found to provide thebest coating results when cured at temperature about 150° C. (300° F.)for 20 minutes. It is a highly significant advantage of the invention,however, that these same coating compositions can withstand, forexample, temperature as high as about 200° C. (390° F.) for periods oftime as long as about 60 minutes. Accordingly, great flexibility isprovided in both designing and implementing a curing schedule for partscoated with the coating compositions of the invention. Thus, in theassembly of automotive vehicles, for example, vehicles unavoidably heldin a curing oven for long periods of time during unplanned assembly lineshut-downs are recovered with cured and unharmed coatings.

High solids coating compositions according to the present invention,comprising the novel crosslinkable hydroxy functional urethane modifiedpolyester resins of the invention, especially the preferred resinsdescribed above and blocked polyisocyanate crosslinking agent,especially the preferred materials described above, have been found toafford cured coatings with improved corrosion resistance and chipresistance, thus representing a highly advantageous advance in the art.

A most preferred use of the coating composition of the invention is as ahigh solids hot sprayable chip resistant primer for use on a bare metalsubstrate such as for an automotive vehicle body which is subject tochipping. Primer compositions typically are pigmented and any pigmentscommonly included in primer compositions for metal substrates andacrylic dispersion topcoats such as, for example, carbon black, ironoxide, lithopone, magnesium, silicate, silica, barium sulfate, TiO₂,chrome yellow, calacium chromate, strontium chromate, zinc potassiumchromate any the like may be used. The primer can be pigmented accordingto known methods including, for example, by grinding pigments in aportion of the curable resin and adding -o the primer composition.

The pigment-to-binder ratio of the chip resistant primer may be fromabout 0.5:1 to about 2:1 by weight, respectively; it is preferred,however, to use a primer having a pigment-to-binder ratio of from about1:1 to about 1.5:1 by weight, respectively.

In preferred embodiments of this invention pigments and thixotropicagents desirably are dispersed with epoxy ester resins which do not havean elastomeric component as does the hydroxy functional urethanemodified polyester resin employed as the primary film forming resin ofthe compositions of this invention. It has been found that, in additionto being very effective dispersing agents for the preparation of pigmentmillbases and thioxtropic dispersions, non-elastomeric epoxies give thecompositions toughness. One type of epoxy useful for this purposecomprises the reaction product of diepoxide, diphenol and/or dimer acidand a mixture of Soya fatty acid and propionic acid (See Example 5).Other epoxy ester resins useful for this purpose are those disclosed inUnited States patent application Ser. Nos. 448,886 filed June 14, 1982(abandoned), 431,465 filed Sept. 30, 1982 (abandoned) and in U.S. Pat.No. 4,491,641 all assigned to the assignee of this application. Theseresins comprise the simultaneous reaction product of diepoxide with (i)diphenol, dicarboxylic acid or a mixture of them in chain extensionreaction and (ii) fatty acid in chain terminating esterificationreaction. Still other suitable epoxy resins useful for dispersingpigment and thixotropic agents will be apparent to the skilled of theart in view of the present disclosure.

No special expedients are necessary in formulating the primercompositions of this invention. For example, they may be prepared simplyby incorporating the resinous components in a suitable solvent system.Thus, for example, by suitable mixing or agitation, each resinouscomponent may be dissolved in a solvent and the resulting solutionscombined to form finished primer compositions.

The solvent system may be any suitable combination of organic solventsas described above. For a high solids, hot sprayable, automotive vehiclechip resistant primer, the solvent will comprise preferably about 20 toabout 40 percent by weight of the total coating compositions, althoughof course, larger or smaller amounts may be utilized depending upon thesolids content desired.

The primer is generally maintained at about 65 to about 80 percentsolids content for hot spraying purposes with conventional thinners suchas aromatic hydrocarbons, commercial petroleum cuts which areessentially aromatic, and the like, and sprayed onto the metal base orother substrate and cured. The primer may be applied in greaterthickness of 1 to 25 mils wet, preferably 10 to 25 mils wet, in order toobtain final coatings in the desired range of 5-11 mils dry in regionshighly susceptible to chipping and is then feathered down in thicknessto the thickness of paints in areas not receiving a chip resistantprimer. The primer is cured at elevated temperatures by any convenientmeans such as baking ovens or banks of intra-red heat lamps. Curingtemperature are preferably from about 135° C. to about 165° C., althoughcuring temperatures from about 100° C. to about 230° C. may be employed,if desired.

Industrial Application

It will be apparent from the foregoing that this invention hasindustrial applicability as a coating composition, especially as a hotsprayable, high solids coating composition suitable for use as a chipresistant automotive vehicle primer adapted for use on body panel areassubject to chipping by stones, gravel and other road debris.

The invention will be further understood by referring to the followingdetailed examples. It should be understood that these specific examplesare presented by way of illustration and not by way of limitation.Unless otherwise specified, all references to "parts" are intended tomean parts by weight.

The following resin examples (1-6) were prepared in a five liter roundbottom flask equipped with a stirrer, reflux condenser, thermometer, andheating mantle. The flask was flushed with dry nitrogen to maintain aninert atmosphere.

EXAMPLE 1 Preparation of Hydroxy-Containing Urethane Modified PolyesterPrecursor

In a suitable reactor were weighed 862 parts xylene, 1070 partsEsterdiol 204 (trademark, Union Carbide, diol), and 0.04 parts dibutyltin dilaurate catalyst. The temperature of the mixture was brought up tothe point where it began to reflux. After one and a half hours, it wascooled to 105° C. 690 parts Desmondur W (trademark, Mobay Chemical Co.,diisocyanate) were added to the mixture over a period of three hours.The mixture was maintained at 110° C. until no residual NCO wasdetected. 454 parts Tone 0301 (trademark, Union Carbide,polycaprolactone triol), 500 parts adipic acid, and 7 parts Fascat 4100(trademark, M&T Chemical Co., catalyst) were added to the mixture. Thetemperature of the mixture was brought up to 155° C. At reflux, 123parts water were collected, the heat was increased to raise thetemperature to 200° C. 700 parts xylene were removed from the mixturewhile reflexing. The reaction was continued until solution acid numberof 6 was reached. The mixture was cooled to 150° C. and 1350 partsmethyl amyl ketone were added. The resulting resin had Y viscosity at60.0% solids.

EXAMPLE 2 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 2600 parts pf the resin made inExample 1. The temperature was raised to 155° C. and the mixture wasrefluxed for half an hour. 800 parts epsilon-caprolactone were added tothe mixture, and the temperature was maintained at 155° C. for twohours. The mixture was allowed to cool. The resulting resin had a Z₂viscosity at 70.0% solids.

EXAMPLE 3 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 2000 parts of the resin made inExample 1. The temperature was raised to 155° C. and the mixture wasrefluxed for half an hour. 1250 parts epsilon-caprolactone and 1 partdibutyltin oxide were added to the mixture. The temperature of themixture was maintained at 155° C. for two hours and then allowed tocool. The resulting resin had a Z₃ viscosity at 75% solids.

EXAMPLE 4 Preparation of Blocked Polyisocyanagte Crosslinking Agent

In a suitable reactor were weighed 1078 parts 2,4-toluene diisocyanate.The temperature was brought up to 45° C. and 700 partsepsilon-caprolactam was added. The temperature slowly began to rise and600 parts Solvesso 150 was added to the mixture. The temperature wasmaintained at 60° C. until an NCO equivalent of 287 was reached. 624parts Tone 0301 (trademark, Union Carbide, polycaprolactone triol) wasadded to the mixture and the temperature was raised to 105°-110° C.After four hours, no residual NCO was detected via titration. 172 partsSolvesso 150 and 829 parts M-pyrol were added to the mixture which wasthen allowed to cool. The resulting resin had a Z₅ viscosity at 60.0%solids.

EXAMPLE 5 Preparation of Epoxy Ester Dispersing Resin

In a suitable reactor were weighed 1280 parts Epon 829 (trademark, ShellChemical Co., diepoxide), 954 parts Empol 1016 (trademark, EmeryIndustries, dimer acid), 364 parts Soya fatty acid, 268 parts2,2-bis-(hydroxymethyl) propionic acid, and 13 parts lithiumneodeconoate. The temperature of the mixture was brought up to about180° C., at which point an exothermic reaction took place that raisedthe temperature to about 200° C. After one hour, the acid number wasfound to be less than 2. 940 parts Solvesso 100 and 305 parts Solvesso150 were added and the mixture was cooled. The resin had a viscosity ofZ₇ at 70.0% solids.

EXAMPLE 6 Preparation of Blocked Polyisocyanate Crosslinking Agent

In a suitable reactor were weighed 870 parts methylethyl ketoxime and180 parts Solvesso 100. 1330 parts of PAPI 27 was added dropwise to themixture over two hours; the reaction temperature rose from roomtemperature to 85°-95° C. 39 parts 2-ethylhexanol was added to themixture and the temperature of the mixture was maintained at 85°-95° C.for one hour. At that point, 816 parts of M-pyrol was added and themixture was cooled. The resulting resin was dark brown and had aviscosity of 6000 cps at 68.0% solids.

EXAMPLE 7 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 354 parts neo-pentyl glycol, 204parts trimethylolpropane, 482 parts adipic acid, 4 parts dibutyl tinoxide, and 50 parts xylene. The temperature was brought up to about 130°C. and a reflux started; the mixture temperature increased to 180° C.and 120 parts of water were collected. At that point, the acid numberwas determined to be 1. 220 parts of M-pyrol was added to the mixture.It then was allowed to cool to 110° C. 6 drops of dibutyl tin dilauratewas added to the mixture. 160 parts Desmodur W (trademark, MobayChemical Co., diisocyanate) then was added dropwise to the mixture over1 hour. The temperature of the mixture was maintained at 120° C. for 1hour. After 1 hour no residual NCO was detected. 1085 partsepsilon-caprolactone was added to the mixture. The temperature wasraised slowly to 175° C. and maintained there for 2 hours. The mixturewas then cooled. 450 parts of M-pyrol was added. The resulting resin wasdark brown in color and had a Z₂ viscosity at 75% solids.

EXAMPLE 8 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 571 parts Esterdiol 204, (trademark,Union Carbide, diol), 500 parts xylene, and 5 drops dibutyl tindilaurate. The temperature of the mixture was brought up to the pointwhere it began to reflux. After 1 hour, it was cooled to 110° C. 356parts Desmodur W (trademark, Mobay Chemical Co., diisocyanate) was addeddropwise over 1 hour and the temperature of the mixture was maintainedat 120° C. After 2 hours, no residual NCO was detected. 240 partstrimethylolpropane, 262 parts azelaic acid, 66 parts adipic acid, and 4parts dibutyl tin oxide were added to the mixture. The temperature ofthe mixture was raised to 145° C. to reflux. 300 parts of xylene wasdistilled from the mixture. The temperature slowly rose to 190° C., and60 parts of water were distilled from the mixture in 2 hours. At thatpoint, the acid number of the mixture was determined to be 1. Themixture was cooled to 170° C. and 2162 parts epsilon-caprolactone wasadded. The temperature was maintained at 175° C. for 2 hours. The heatwas removed and 990 parts M-pyrol was added to the mixture and it wasthen allowed to cool. The resulting resin was dark brown in color andhad a viscosity of Z at 75% solids.

EXAMPLE 9 Preparation of Hydroxy-Containing Urethane Modified PolyesterPrecursor

In a suitable reactor were weighed 714 parts Esterdiol 204 (trademark,Union Carbide, diol), 220 parts trimethylolpropane, 2002 parts Empol1016 (trademark, Emery Ind., dimer acid), 100 parts xylene, and 5 partsdibutyl tin oxide. The temperature of the mixture was raised to 160° C.Water was distilled slowly from the mixture. The temperature rose to200° C. and 120 parts of water were collected. At that point, themixture had an acid number of 1.6. 921 parts M-pyrol was added and themixture was cooled to 115° C. 337 parts Desmodur W (trademark, MobayChemical Co., diisocyanate) was added dropwise over 1 hour to themixture. The resulting resin had a Z₆ viscosity at 72.8% solids.

EXAMPLE 10 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 2349 parts of the resin made inExample 9 and 726 parts epsilon-caprolactone. The temperature of themixture was raised to 175° C. and maintained there for 2 hours. At thatpoint, 380 parts of M-pyrol was added and the mixture was cooled. Theresulting resin had a Z₄ viscosity at 69.2% solids.

EXAMPLE 11 Preparation of Hydroxy-Containing Urethane Modified PolyesterPrecursor

In a suitable reactor were charged 718 parts Esterdiol 204 (trademark,Union Carbide, diol), 506 parts xylene and 0.05 parts dibutyl tindilaurate. The temperature of the mixture was brought up to the pointwhere it began to reflux. After 1 hour, it was cooled to 110° C. and 464parts of Desmodur W (trademark, Mobay Chemical Co., diisocyanate) wasadded dropwise to the mixture over 1 hour. The mixture was maintained at115° C. until no residual NCO was detected. 104 partstrimethylolpropane, 1207 parts Empol 1016 (trademark Emery Ind., dimeracid), and 4 parts dibutyl tin oxide were added to the mixture. Thetemperature was raised to 160° C., and 350 parts of xylene and 80 partsof water were collected. The temperature of the mixture was allowed torise to 200° C. An additional 50 parts of xylene and 20 parts of waterwere removed. At that point, an acid number of 3.5 was determined. 936parts M-pyrol were added and the mixture was allowed to cool. Theresulting resin was brown in color and had a Z₂ viscosity at 69.2%solids.

EXAMPLE 12 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 1942 parts of the resin made inExample 11 and 407 parts epsilon-caprolactone. The temperature of themixture was raised to 175° C. and maintained there for 2 hours. 757parts M-pyrol was added and the mixture was allowed to cool. Theresulting resin had a Z viscosity at 56.4% solids.

EXAMPLE 13 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were weighed 648 parts Esterdiol 204 (trademark,Union Carbide, diol), 456 parts xylene, and 5 drops dibutyl tindilaurate. The temperature was brought to the point where the mixturebegan to reflux. After one hour of refluxing, it was cooled down to 110°C. and 276 parts of toluene diisocyanate were added dropwise to themixture over 1 hour. The temperature was maintained at 115° C. until noresidual NCO was detected. 240 parts Tone 0301 (trademark, UnionCarbide, polycaprolactone triol), 263 parts adipic acid, and 3 partsFascat 4100 (trademark, M&T Chemical Co., catalyst) were added to themixture. The temperature of the mixture was raised to 155° C. and refluxstarted. The temperature of the mixture continued to rise to 175° C. and65 parts water were distilled off. At that point, the mixture had anacid number of 1.5. 1364 parts epsilon-caprolactone and 1.4 partsdibutyl tin oxide were added to the mixture. The temperature wasmaintained at 175° C. for 2 hours. 908 parts M-pyrol were added and themixture was allowed to cool. The resulting resin had a Y viscosity at73.4% solids.

EXAMPLE 14 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor were charged 931 parts Esterdiol 204 (trademark,Union Carbide, diol), 266 parts trimethylolpropane, 668 parts adipicacid, 50 parts xylene, and 5 parts dibutyl tin oxide. The temperature ofthe mixture was brought up to reflux at 155° C. and the temperature wasallowed to rise to 175° C. 166 parts of water was distilled from themixture. At that point, the mixture had an acid number of 2.0. 764 partsxylene were added and the mixture was cooled to 110° C. 200 partstoluene diisocyanate were added over 1 hour. The temperature wasmaintained at 115° C. until no residual NCO was detected. 1900 partsepsilon-caprolactone and 2 parts dibutyl tin oxide were added to themixture. The temperature was raised to 170° C. and maintained for 3hours. 450 parts M-pyrol was added and the mixture was allowed to cool.The resulting resin had a V viscosity at 73.4 % solids.

EXAMPLE 15 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor are weighed 459 parts Esterdiol 204 (trademark,Union Carbide, diol), 310 parts Tone 0301 (trademark, Union Carbide,polycaprolactone triol), 423 parts azelaic acid, 4 parts dibutyl tinoxide, and 50 parts xylene. The temperature is raised slowly to 175° C.and 81 parts of water are removed. 476 parts xylene and 4 drops dibutyltin dilaurate are added and the mixture is allowed to cool to 110° C.190 parts Desmodur W (trademark, Mobay Chemical Co., diisocyanate) isadded dropwise over 1 hour and the temperature is maintained at 115° C.until no residual NCO is detected. The temperature of the mixture israised to reflux and 276 parts xylene are removed. 1301 partsepsilon-caprolactone is added to the mixture. The temperature of themixture is raised to 175° C. and maintained for 2 hours. 667 partsM-pyrol are added and the mixture is allowed to cool.

EXAMPLE 16 Preparation of Hydroxy Functional Urethane Modified PolyesterResin

In a suitable reactor are weighed 225 partsdimethyl-1,4-cyclohexanedicarboxylate, 164 parts adipic acid, 310 partsTone 0310 (trademark, Union Carbide, polycaprolactone triol), 459 partsEsterdiol 204 (trademark, Union Carbide, diol), 4 parts dibutyl tinoxide, and 50 parts xylene. The temperature is raised slowly to 175° C.72 parts of methanol and 40 parts of water are collected. 400 partsxylene and 0.05 parts dibutyl tin dilaurate are added and the mixture iscooled to 110° C. 180 parts Desmodur W (trademark, Mobay Chemical Co.,diisocyanate) is added over 1 hour and the mixture is maintained at 115°C. until no residual NCO is observed. 1900 parts epsilon-caprolactone isadded and the temperature of the mixture is raised to 175° C. It ismaintained there for 2 hours. 600 parts M-pyrol is added and the mixtureis cooled.

EXAMPLE 17 Preparation of Blocked Polyisocyanate Crosslinking Agent

In a suitable reactor were weighed 1080 parts Desmodur L-2291(trademark, Mobay Chemical Co., biurette of hexamethylene diisocyanate)and 0.08 parts dibutyl tin dilaurate. 542 parts methyl ethyl ketoximewas added dropwise over 1 hour. The temperature of the mixture wasallowed to rise slowly from room temperature to 90° C. The mixture wasmaintained at that temperature until no residual NCO was detected. 400parts methyl amyl ketone was added and the mixture was allowed to cool.

EXAMPLE 18 Bentone Gel Preparation

To a clean Ball Mill were charged the following:

    ______________________________________                                                               Parts                                                  ______________________________________                                        Solvesso 150             513                                                  Propylene Carbonate       13                                                  Bentone 38                30                                                  Grind 30 minutes, then add:                                                                            384                                                  Resin of Example 5                                                            Grind approximately 2 hours to 8 Hegman                                                                 60                                                  Letdown with:                                                                 Solvesso 150                                                                  Roll 30 minutes and drop immediately                                          This material is thixotropic.                                                 ______________________________________                                    

EXAMPLE 19 Millbase Preparation

In a one gallon can or ball mill were charged the following materialsand one quart of diagonal shot. The mixture was placed on roller millfor 16-24 hours to reach a 7+ Hegman dispersion. At that point, theletdown was added and the mixture was run an additional hour on theroller mill.

    ______________________________________                                                        Parts                                                         ______________________________________                                        Toluene           585                                                         2-Ethyl Hexanol    95                                                         Polyethylene Wax   70                                                         Anti-Terra U*      40                                                         Resin of Example 5                                                                              103                                                         Barytes           2259                                                        TiO.sub.2         429                                                         Carbon Black       29                                                         Strontium Chromate                                                                              143                                                         Letdown:          247                                                         Resin of Example 5                                                            ______________________________________                                         *Trademark of Byk Malline Krodt, Wallingford, CT. 06492, AntiTerra U is a     antisettling and wetting agent.                                          

EXAMPLE 20-23

Coating compositions according to the invention are formulated as shownbelow.

    ______________________________________                                                        Example                                                                       20   21       22     23                                       Composition       Parts                                                       ______________________________________                                        Millbase of Example 19                                                                          295    422      295  295                                    Resin of Example 2                                                                              349    221                                                  Resin of Example 3                292  360                                    Crosslinker of Example 4                                                                        228    209      266                                         Crosslinker of Example 6               165                                    Bentone gel of Example 18                                                                       133    133      133  133                                    M--pyrol           14     15       14   47                                    ______________________________________                                    

The coating composition are prepared by sequential mixing in a 5 gallonworking capacity EMCO Proto-Lab SW Mill (trademark, Epworth Mfg. Co.,South Haven, Mich.), set at 900 rpm. The millbase, resin, crosslinker,M-pyrol are added sequentially while mixing.

The above compositions are sprayed at 140° C.-160° C. using hot-sprayequipment commercially available from Nordson Corp. Unpolished Bonderitesteel panels are sprayed and baked at 155° C. for 20 minutes. Thethickness of the coating tested varies from 5 mils to 12 mils. Thepanels are top-coated with white enamel and tested for chip resistanceusing 10 pts. of gravel in the gravelometer test. All the abovecompositions exhibit excellent chip resistance. In addition, panels aretested for corrosion resistance (500 hrs. salt spray test, scribedpanels) and humidity resistance with excellent results.

    __________________________________________________________________________    Examples 24-33                                                                Additional coating compositions according to the invention are shown          below.                                                                                     Example                                                                       24 25 26 27 28 29 30 31 32 33                                                    Composition (Parts)                                           __________________________________________________________________________    Millbase of Example 19                                                                     390                                                                              390                                                                              390                                                                              390                                                                              390                                                                              390                                                                              390                                                                              390                                                                              390                                                                              390                                   Resin of Example 5                                                                          72                                                                               72                                                                               72                                                                              72 72  72                                                                               72                                                                               72                                                                               72                                                                               72                                   Resin of Example 2                                                                         280                                                              Resin of Example 3                                                                            260                                                           Resin of Example 7 317                                                        Resin of Example 8    317                                                     Resin of Example 10      280                                                  Resin of Example 12         346                                               Resin of Example 13            275                                            Resin of Example 14               270                                         Resin of Example 15                  265                                      Resin of Example 16                     260                                   Crosslinker of Example 4                                                                   244                                                                              244            244                                                                              244                                                                              244                                                                              244                                   Crosslinker of Example 6                                                                         144                                                                              144                                                     Crosslinker of Example 17                                                                              175                                                                              175                                               Cab-O-Sil*    12                                                                               12                                                                               12                                                                              12 12  12                                                                               12                                                                               12                                                                               12                                                                               12                                   n-butyl acetate                                                                             70                                                                               90                                                                               75                                                                              95 76  70                                                                               70                                                                               65                                                                               85                                                                               80                                   __________________________________________________________________________     *Trademark, Cabot Corp., Boston, Mass.; CabO-Sil is a fumed silica            (antisettling agent).                                                    

In view of this disclosure, many modifications of this invention will beapparent to those skilled in the art. It is intended that all suchapparent modifications fall within the true scope of this invention andbe included within the terms of the appended claims.

What is claimed is:
 1. A hydroxy functional urethane modified polyesterresin suitable for use in a thermosetting composition, which resin has anumber average molecular weight (M_(n)) of between about 2,000 and about20,000, said resin being the product of polymerization at about 50°-300°C. of a reaction mixture of lactone monomers in the presence ofhydroxy-containing urethane modified polyester precursor (i) having anumber average molecular weight (M_(n)) between about 1,000 and about10,000, (ii) having a hydroxyl number between about 30 and about 300,(iii) containing between about 1 and about 10 urethane groups permolecule; wherein pendant hydroxyl terminated polycaprolactone moietiesare formed and attached to the polyester precursor and wherein saidlactone monomers are selected from those represented by the generalformula: ##STR5## in which n is at least 4, at least n+2 R's arehydrogen, and the remaining R's are substituents selected from the groupconsisting of alkyl, cycloalkyl, alkoxy and single ring aromatichydrocarbon radicals, and wherein said hydroxy-containing urethanemodified polyester precursor is the reaction product of:(A) urethanemodified diol being the reaction product of:(a) diol and (b)diisocyanate, wherein said diol and said diisocyanate are reacted in amolar ratio from about 4:1 to about 4:3, respectively; (B) polyolcomprising at least about 5 weight percent triol; and (C) acid componentselected from dicarboxylic acids and anhydrides thereof and wherein thereaction mixture comprises between about 10 and about 80 weight percentsaid hydroxy-containing urethane modified polyester precursor andbetween about 90 and about 20 weight percent said lactone monomers.
 2. Ahydroxy functional urethane modified polyester resin in accordance withclaim 1, wherein said percursor has a number average molecular weight(M_(n)) between about 2000 and about
 4000. 3. A hydroxy functionalurethane modified polyester resin in accordance with claim 1, whereinsaid precursor has a hydroxyl number between about 30 and about
 200. 4.A hydroxy functional urethane modified polyester resin in accordancewith claim 1, wherein said polyol further comprises diol.
 5. A hydroxyfunctional urethane modified polyester resin in accordance with claim 1,wherein said acid component is selected from the group consisting of C₆-C₄₀ dicarboxylic acids and anhydrides thereof.
 6. A hydroxy functionalurethane modified polyester resin in accordance with claim 1, whereinsaid monomers comprise unsubstituted epsilon-caprolactone monomers.